Large Chiral Orbital Texture and Orbital Edelstein Effect in Co/Al Heterostructure

TL;DR

This paper reveals a large chiral orbital texture and orbital Edelstein effect at Co/Al interfaces, explaining enhanced current-induced torques through orbital Rashba effects and surface states, advancing orbital transport understanding.

Contribution

It uncovers the orbital Rashba effect and helical orbital texture at Co/Al interfaces, providing a theoretical basis for large torques observed experimentally.

Findings

Large helical orbital texture at Co/Al interface

Orbital Rashba effect causes orbital accumulation

Enhanced current-induced torques explained by orbital effects

Abstract

Recent experiments by S. Krishnia et al., Nano Lett. 23, 6785 (2023) reported an unprecedentedly large enhancement of torques upon inserting thin Al layer in Co/Pt heterostructure that suggested the presence of a Rashba-like interaction at the metallic Co/Al interface. Based on first-principles calculations, we reveal the emergence of a large helical orbital texture in reciprocal space at the interfacial Co layer, whose origin is attributed to the orbital Rashba effect due to the formation of the surface states at the Co/Al interface and where spin-orbit coupling is found to produce smaller contributions with a higher-order winding of the orbital momentum. Our results unveil that the orbital texture gives rise to a non-equilibrium orbital accumulation producing large current-induced torques, thus providing an essential theoretical background for the experimental data and advancing the use of orbital transport phenomena in all-metallic magnetic systems with light elements.